Xi1 Canis Majoris

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ξ1 Canis Majoris
Canis Major constellation map.svg
Red circle.svg
Location of ξ1 Canis Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension  06h 31m 51.36636s[1]
Declination −23° 25′ 06.3181″[1]
Apparent magnitude (V) 4.33 - 4.36[2]
Spectral type B1 III[3]
U−B color index −0.98[4]
B−V color index −0.24[4]
Variable type β Cep[3]
Radial velocity (Rv)−26.9[5] km/s
Proper motion (μ) RA: −2.91[1] mas/yr
Dec.: +6.22[1] mas/yr
Parallax (π)2.36 ± 0.20[1] mas
Distance1,400 ± 100 ly
(420 ± 40 pc)
Absolute magnitude (MV)−3.86[6]
Mass14.2±0.4[6] M
Radius7.9±0.6[6] R
[6] L
Surface gravity (log g)3.78±0.07[6] cgs
Temperature27000±1000[6] K
Metallicity [Fe/H]−0.18[7] dex
Rotational velocity (v sin i)0[6] km/s
Age11.1±0.7[6] Myr
Other designations
ξ1 CMa, 4 Canis Majoris, CD−23°3991, GC 8496, HD 46328, HIP 31125, HR 2387, SAO 171895, ADS 5176, CCDM 06319-2325
Database references

Xi1 Canis Majoris, Latinized from ξ1 Canis Majoris, is a Beta Cephei variable star in the constellation Canis Major. It is approximately 1,400 light years from Earth.

ξ1 Canis Majoris is a blue-white B-type star. It has generally been assigned a luminosity class of III (giant) or IV (subgiant), for example B1III[3] or B0.5IV.[6] Comparison of its properties with model evolutionary tracks suggest that it is a main sequence star about three quarters of the way through its main sequence lifetime.[6]

The apparent magnitude varies from +4.33 to +4.36 with a period of 5.03 hours.[2] Its pulsations cause its radius to vary by 1.0% to 1.5%. At the same time its effective temperature by about 500 K above and below its mean temperature.[6]

ξ1 Canis Majoris has the longest known rotation period of any B class star, taking around 30 years to complete one revolution on its axis.[8] This is thought to be due to magnetic braking; ξ1 Canis Majoris has the strongest magnetic field of any β Cephei star and would be expected to spin down completely in around four million years. It also has the strongest and hardest X-ray emission of any β Cephei star.[6]

ξ1 Canis Majoris forms a naked eye pairing with ξ2 Canis Majoris a little less than a degree away. The Washington Double Star Catalog lists two 14th magnitude companions about 27 away.[9] In addition, an unseen close companion is suspected due to some faint emission lines in the spectrum that are best explained by a Be star invisible against the brighter primary.[6]


  1. ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. ^ a b "International Variable Star Index". Retrieved 2018-11-13.
  3. ^ a b c Hubrig, S.; et al. (January 2009). "New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars". Astronomische Nachrichten. 330 (4): 317. arXiv:0902.1314. Bibcode:2009AN....330..317H. doi:10.1002/asna.200811187.
  4. ^ a b Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  5. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. Determination of Radial Velocities and Their Applications. 30. p. 57. Bibcode:1967IAUS...30...57E.
  6. ^ a b c d e f g h i j k l m Shultz, M.; Wade, G. A.; Rivinius, Th.; Neiner, C.; Henrichs, H.; Marcolino, W.; MiMeS Collaboration (2017). "The pulsating magnetosphere of the extremely slowly rotating magnetic β Cep star ξ1 CMa". Monthly Notices of the Royal Astronomical Society. 471 (2): 2286. Bibcode:2017MNRAS.471.2286S. doi:10.1093/mnras/stx1632.
  7. ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015.
  8. ^ Shultz, M.; Kochukhov, O.; Wade, G. A.; Rivinius, Th (2018). "The pulsationally modulated radial crossover signature of the slowly rotating magnetic B-type star ξ1 CMa". Monthly Notices of the Royal Astronomical Society. 478 (1): L39. arXiv:1804.07535. Bibcode:2018MNRAS.478L..39S. doi:10.1093/mnrasl/sly070.
  9. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.